1. Field of Invention
The invention relates to a thread tying method and a thread tying apparatus which are used in various textile machines, such as a weaving machine, a knitting machine, a thread winding machine, and an embroidery machine.
2. Description of Related Art
Conventionally, various thread tying apparatuses for tying two threads at their ends have been developed. For example, Japanese Patent Publication No. 54-31544 discloses an apparatus for tying two threads at their ends using an overhand knot. In this apparatus, the thread ends are pneumatically sucked into a thread introducing pipe. The pipe includes first and second hooks required for thread tying therein. The first hook is attached to a ring, which is rotatable and vertically movable, and the second hook is disposed in a loop formation cylinder, which is disposed in the inside diameter of the ring, so as to be vertically movable. A thread catching portion is provided on a part of an upper end of the loop formation cylinder. A pair of thread guides in front of and behind the ring and a pair of chucking units outside the thread guides are disposed in a line. A tightening lever is disposed between the thread guide and the chucking unit, which are at the side where the threads enter. A thread cutter is disposed outside the other chucking unit, and a pair of U-rings for pulling threads are positioned to have the other elements placed therebetween.
In the above structure, the sucked thread ends pass through the U-rings. When the U-rings are moved downward, both thread ends are held in a line by the chucking units placed therebetween, and pulled into the first hook by way of the thread guides on both sides, and supported by the chucking units. After any unnecessary portion is cut from each thread end by a thread cutting unit, the thread ends pulled into the first hook are wound around the loop formation cylinder upon the rotation of the ring and the upward movement of the first hook. After the thread ends, caught in the first hook, pass the thread catching portion, the second hook is moved up to catch the thread ends, and moved down. Relatively, the thread release lever is moved upward to remove the thread ends from the front chucking unit. When the thread ends are released, the thread tightening lever is moved downward to tighten a loop at the thread catching portion, thereby forming a knot. However, this knot becomes untied easily.
On the other hand, in a weaver""s knot formation method disclosed in Japanese Patent Publication No. 53-18612, a first thread currently used and a second thread, which remain disposed in parallel to each other under a tense condition, are tied at their middle portions. However, in a case where thread change (thread color change) is performed on an embroidery machine, the trail end of the first thread and the beginning end of the second thread are released, and it is impossible to tie the threads at their ends with this technique.
The invention provides a method and an apparatus for tying threads by a weaver""s knot, which ensures firm tightening.
According to an aspect of the invention, in a method for tying a first thread and a second thread, a first loop and a second loop are made from the first thread with a tail end thereof being held, a beginning end of the second thread is inserted into the second loop, and the first loop is reduced to tie the first thread and the second thread. With this method, a weaver""s knot can be made easily and simply.
According to another aspect of the invention, the method may include the following steps: making the first loop from the first thread with the tail end thereof being held using the latch needle having the hook and the latch; making the second loop from the first loop; and reducing the first loop while inserting the beginning end of the second thread into the second loop, to form the weaver""s knot. In such a manner, the use of the latch needle can simplify a thread tying.
According to a further aspect of the invention, a thread tying apparatus may include a first thread holding member that holds a tail end portion of a first thread, a latch needle having a hook at a tip thereof and a latch whose root is pivotally mounted to a stem thereof so as to open and close the latch with respect to the hook, a first loop controller that slidably makes contact with the stem of the latch needle and moves in a direction of an axis of the latch needle, a second thread holding member that holds a beginning end of a second thread and changes a position of the beginning end of the second thread so as to be close to the hook of the latch needle, and an interlock mechanism that performs the following steps: rotating the latch needle on the axis thereof to make a first loop at the hook by winding the first thread substantially around the hook; advancing the latch needle to place the first loop over the latch of the latch needle, which is away from the hook, on the stem of the latch needle and to place a portion extending from the first loop of the first thread inside the latch; moving the first loop controller and the latch needle relative to each other to make the first loop go over the hook, passing the portion extending from the first loop through the first loop, making a second loop at the hook, and making the second loop go over the latch to move the second loop toward the stem of the latch needle; bring the second thread whose beginning end is held at the second thread holding member to the hook; operating the latch needle and the first loop controller together to move the second loop away from the hook and insert the second thread into the second loop; and reducing the second loop and the first loop until the beginning end of the second thread is stopped into the first loop. In this arrangement, the interlock mechanism activates the latch needle, the first thread holding member, the second thread holding member, and the first loop controller respectively in predetermined times, which ensures a thread tying.
According to another aspect of the invention, the apparatus may further include a magnet so as to separate the latch from the hook only when the latch needle comes to a rotated position. As the magnet allows the latch, which is universally pivotable and whose position is unstable, to open when the latch needle is rotated and the latch approaches the magnet, and to keep its position stable, the formation of the first loop can be ensured.
According to a further aspect of the invention, in the thread tying apparatus, the latch may be made of magnetic material so as to open away from the hook when it comes to the rotated position. The adoption of such a material can simplify the structure of the latch.
According to another aspect of the invention, in the apparatus, when the interlock mechanism disposes a portion extending to the first loop of the first thread inside the latch which is open, it places the latch away from an intersecting portion of the first loop, moves the latch needle backward with the latch being kept open by a latch regulating member until a tip of the latch passes the portion extending to the first loop, and rotates the latch needle so that the latch comes close to the intersecting portion of the first loop. This ensures the formation of the second loop.
According to a further aspect of the invention, in the apparatus, a guiding groove is formed on the stem of the latch needle along the axis of the latch needle so that a tip of the first loop controller that moves forward along the guiding groove goes into the first loop. With this structure, when the second loop is made from the first loop, a thread length required to keep a diameter of the first loop can be secured and the first loop is not moved along with back and forth movement of the latch needle. As a result, a thread tying can be performed in place.
According to another aspect of the invention, the apparatus may further include a thread volume controller that secures a thread length required for forming the first loop and the second loop from the first thread and that pulls a midpoint of the first thread to reduce a diameter of the second loop formed at the hook. Even when the tail end of the first thread is held by the first thread holding member, the required thread length can be secured simply, and the second thread to be tied to the first thread can be brought into the second loop without fail.
According to a further aspect of the invention, in the apparatus, the interlock mechanism activates the first thread holding member and the second thread holding member so as to hold and release each end portion of the first thread and the second thread, and the interlock mechanism controls the first thread holding member, the second thread holding member, and the hook such that a relative position between the first thread holding member and the hook is selectively changed between a position where the first thread is supplied and a position where the first thread is not supplied, and such that a relative position between the second thread holding member and the hook is selectively changed between a position where the second thread is supplied and a position where the second thread is not supplied. In this structure, when the latch needle is moved in a direction where the latch needle intersects an axis of each of the threads, the threads can be brought close to the hook and the latch of the latch needle to be involved in the thread tying operation only when necessary.
According to a further aspect of the invention, in the apparatus, the interlock mechanism activates the second thread holding member so as to place the second thread within a path where the latch is rotated before the second loop is moved away from the latch toward the stem of the latch needle. Although the latch is apt to move out of place, this allows the second thread to move to the hook before the latch is closed, and allows the hook of the latch needle to catch the second thread when the second loop comes off the hook.
According to a further aspect of the invention, in the apparatus, the interlock mechanism performs the following steps: advancing the latch needle to move the second loop over the latch toward the stem of the latch needle; making the hook catch the second thread whose beginning end is held at the second thread holding member; moving the latch needle backward to close the latch by the second loop; releasing the beginning of the second thread from the second thread holding member; inserting the second thread into the second loop coming off the hook; and reducing the second loop and the first loop until the beginning end of the second thread is stopped into the first loop, to tie the first thread and the second thread. In this structure, the second thread is released after the latch, which is open, is closed by the second loop to be formed into a weaver""s knot. The closing of the latch can prevent the second thread from coming off the hook, thereby ensuring the insertion of the second thread into the second loop, and realizing that the first loop and the beginning end of the second thread are tied at the second loop which is to take the shape of straight line later.
According to another aspect of the invention, in the apparatus, the beginning end of the second thread is inserted into the second loop coming off the latch needle and held by the second thread pressing device. This can reliably prevent the beginning end of the second thread from coming off the second loop at the final step of thread tying.
According to a further aspect of the invention, in the apparatus, the first thread holding member includes a pair of outside plates, and an inner plate, which is capable of entering between the pair of outside plates, the pair of outside plates and the inner plate are structured to hold the first thread firmly between them, a cutter is disposed which slidably makes contact with one of the pair of outside plates, and the one of the pair of outside plates includes a control part that prevents displacement of the first thread. In such a structure, the tail end portion of the first thread can be firmly held with a short length. When the first thread is cut between the one of the pair of outside plates and the cutter, the displacement of the first thread can be prevented.